Tissue expanders are well known in the art. Traditional tissue expanders are temporarily implanted beneath skin and subcutaneous tissue of humans or animals to create a void or pocket or to stretch the skin. The implanted device is gradually inflated by injecting therein fluid or gel to force the surrounding and overlying skin to expand. Once the skin is expanded and a skin flap has formed, the device is deflated and surgically removed. A permanent, implantable device such as a mammary implant or prosthesis may be placed surgically beneath the skin flap. The expanded skin can also be excised and used in repairing a defective area in another part of the body. For detailed description of tissue expanders, see, e.g., Cohen, J. Dermatol. Sur. Oncol. 19:614-615 (1993); Hammond, et. al., Plastic and Reconstructive Surgery, 92(2):255-259 (1993); Walton and Brown, Annals of Plastic Surgery 30(2):105-110 (1993); Kenna, et al., Annals of Plastic Surgery 32:346-349 (1994). Tissue expanders have also been used in other surgery procedures. For example, tissue expanders may be implanted and inflated at a bleeding site to maintain pressure on the surface to prevent further bleeding while clotting and healing takes place. In addition, tissue expanders have also been implanted within the pelvis of patients who have had some or all of the pelvic contents removed due to cancer. In this situation, the expander excludes the small bowel from the pelvis. As a result, the small bowel which is sensitive to ionizing radiation is excluded from subsequent radiation treatment fields. See, e.g., Keno et. al., Oncology, 12(1):51-54 (1998).
In the above described applications, because the purpose is to stretch or force tissue apart or to simply fill a void, the deflation and removal of the expander generally does not significantly disrupt the surrounding areas and does not cause substantially adverse effect. Nevertheless, the removal of the expander may require an additional surgical procedure.
Tissue expanders have also been used in tissue reconstruction which involves increase of new tissue mass. For example, U.S. Pat. No. 5,716,404 to Vacanti et al. teaches applying traditional expanders in breast reconstruction involving cell transplantation. In this application, cells are injected into the area where new tissue is desired. Prior to the injection, the space for accommodating these cells is created using a tissue expander. The tissue expander is implanted in a collapsed configuration, and is then inflated by introducing therein liquid or gel. Prior to each subsequent injection of cells, the tissue expander is deflated to vacate a space equivalent to the volume of the cell suspension to be injected. Once the space is filled with cell suspension or new tissue, the tissue expander is surgically removed using anesthetic incisions.